For the study, the researchers looked at the effects of chlorogenic acid and surfactin on the individual compounds in HepG2 cells, a human liver cancer cell line. Chlorogenic acid is a bioactive component in green coffee, while surfactin is a cyclic lipopeptide produced and secreted by Bacillus subtilis strains.

The results showed that fermented green coffee beans contained about 20 percent more chlorogenic acid and 26 percent more surfactin than non-fermented extracts. Individually, chlorogenic acid and surfactin exhibited low levels of cytotoxicity against HepG2 cells. However, fermented green coffee bean extracts containing high levels of both chlorogenic acid and surfactin effectively inhibited apoptosis (cell death) caused by oxidative stress and activated cell proliferation. The researchers also found various bioactive compounds in the fermented green coffee beans that played a role in cell proliferation and cytotoxicity.

Do fermented green coffee beans suit consumers’ taste?

In a study published in the Journal of Food Quality, a team of researchers from South Korea examined the antioxidant activity and consumer acceptance of yeast-fermented green coffee beans. For their study, they fermented green coffee beans for 24 hours using three different yeast strains to increase the beans’ functionality.

The research team looked at the resulting physicochemical properties, antioxidant activity, total polyphenol and flavonoid contents, and consumer acceptability of fortified green coffee beans. The results showed that the yeast fermentation effectively enhanced the functionality of green coffee beans by dramatically increasing the beans’ antioxidant activity.

In addition, the team found that the total polyphenol and total flavonoid content of the yeast-fermented green coffee beans were significantly higher than regular beans. However, consumer acceptance for the fermented green coffee beans was slightly lower than that of regular ones. This may be because of the fermentation process affecting the aroma and flavor of the coffee beans.

Nonetheless, nearly 40 percent of consumers significantly liked one of the fermented green coffee beans more than the controls, according to agglomerative hierarchical clustering analysis. These consumers reported that fermenting with yeast did not give the green coffee beans a bad odor or flavor.

They also found the high antioxidant activity and phenolic compounds of the yeast-fermented beans appealing. They suggested that more people would be willing to try the fermented coffee beans if they were aware of the beans’ improved functionality.